it may contain single ways as well if there are few between one country and France (France / Monaco could have been represented by two ways only)

The sum of its ways, relation's ways and relation's relation's ways should form one or more closed polygon(s) that represent France's boundaries. (just like the Relation:multipolygon relations). It should not contain relation members that are administrative subdivisions (admin_level 3 or more). It means it shouldn't contain "inside" boundaries, just the outlines of France.

in the multiple country relation such as territorial borders, water borders.

Special cases

Where to put enclaves of a country ?

Enclaves should be child member of the boundary relation, not member of the boundary segment.

Should the boundary relations only form one continuous line ?

No. For exemple, in the case of the France/Spain boundary, Andorra is a country that cuts this boundary in two, anyway, those two lines are to be put in the same boundary segment relation (but they could be relations themself as well, but France and Spain will only have one "France/Spain" boundary and only one relation for that)

Don't delete the traditional non pyramidal relation

Please do not delete the "traditional method" boundary if you use the pyramidical construction, since mapmakers around the world rely on the consistency of the "traditional method" for the country boundaries they use worldwide.

Unfortunately, this is easy to ask, but harder to do ! Technical limitations of the OSM editing servers makes it almost impossible (specially to non power users) to edit some huge relation made with the "traditional method". I guess the traditional relations should be kept as long as possible until data consumers update their software, but when editing become impossible, they will be dropped because my view is that editing has priority over consumers sletuffe 15:24, 5 May 2012 (BST)